The aim of the proposed research is to investigate certain aspects of the control of gene expression in mammalian and other eukaryotic cells. We propose to extend our studies of the role of nuclear ribonucleoprotein complexes in the processing of nuclear RNA and the transport of messenger-RNA from nucleus to cytoplasm. We have previously purified the 30S ribonucleoprotein subcomplex of mouse ascites tumor cells, which contains the bulk of the heterogeneous nuclear RNA including mRNA, and have isolated a smaller complex (ca 15S) which, we have found, contains polyadenylate sequences (poly A) in these tumor cells. The protein components of these complexes have been identified, and antisera to some of them have been raised in rabbits. We will use antibodies purified from these sera to further study the function of these complexes in normal resting and stimulated tissues (regenerating liver, for example) and in neoplastic cells. The possible involvement of the proteins of the complexes in post-transcriptional modulation of gene expression will be assesed. Biochemical studies will investigate the structure of the protein components of ribonucleoprotein complexes and the basis for their selective interaction with RNA species. We also intend to define the nature of a common nuclear RNA sequence which we have found to be linked to oligo-adenylate in nuclear complexes. Electron microscope studies will be continued to define the morphology of RNA:protein complexes and their subunits.